Variable length electrodes for delivery of irrigated ablation

ABSTRACT

A device for ablating tissue is provided. The device comprises a conductive element with a channel for irrigating fluid formed therein, which is in contact with a non-conductive microporous interface. All or a portion of the interface may be removable. When the interface is removed, a portion of the conductive element is exposed for use in ablating tissue. Methods of using the device and of removing the interface are also provided.

FIELD OF THE INVENTION

[0001] This invention relates to ablation devices that are used tocreate lesions in tissue. More particularly, this invention relates toconductive elements for use in such devices which vary in length andwhich incorporate improved methods of irrigation delivery.

BACKGROUND OF THE INVENTION

[0002] The action of the heart is known to depend on electrical signalswithin the heart tissue. Occasionally, these electrical signals do notfunction properly. The maze procedure is a surgical operation forpatients with chronic atrial fibrillation that is resistant to medicaltreatment. In this procedure, incisions are created in the right andleft atria to produce an orderly passage of the electrical impulse fromthe SA node to the atrioventricular node. Blind passageways are alsocreated to suppress reentry cycles. Currently, the lesions may still becreated using a traditional cut and sew technique. The scar tissueresulting from the procedure results in a non-conductive lesion.

[0003] Ablation of cardiac conduction pathways in the region of tissuewhere the signals are malfunctioning is now being used to replace thesurgical incisions. Ablation is also used therapeutically with otherorgan tissue, such as the liver, prostate and uterus. Ablation oforganic tissue is also used in several surgical procedures, for bothdiagnosis and therapy.

[0004] In one type of procedure, one or more electrodes at the tip of anelectrophysiology ablation device allow the physician to measureelectrical signals along the surface of the heart (mapping). Whennecessary, in another type of procedure, the physician can also ablatecertain tissues using, typically, radio frequency (RF) energy conductedto one or more ablation electrodes. During tissue ablation, energy isused to create lesions in the tissue for different purposes. High levelsof energy are used to cut and remove tissue (electrosurgery). Lowerlevels of energy are used to cause cell damage but leave the structureintact so that electrical pathways are blocked within the tissue.

[0005] A variety of devices, such as catheters, are used to ablatetissue. Typically, such devices include a conductive tip, which servesas one electrode in an electrical circuit. The electrical circuit iscompleted via a grounding electrode that may also be on the device ormay be coupled to the patient. By controlling the level of energytransmitted to the electrode, the surgeon is able to control the amountof heat generated for the purposes described above.

[0006] Irrigation of the ablation site cools the electrode. Irrigatedablation is also known to create deeper lesions that are more likely tobe transmural. Transmurality is achieved when the full thickness of thetarget tissue is ablated.

[0007] During ablation, irrigation of the ablation site helps to coolthe ablation electrodes, thereby reducing overheating in the vicinity ofthe electrodes. Undesirable consequences of overheating include theexcessive coagulation of blood and the unintended destruction of healthytissue adjacent the ablation site. The efficient cooling of the linearablation electrode permits longer lesions to be created by permittinghigher ablation energy without resulting in excessive electrode heating.

[0008] Typically, delivery of irrigation to the site is accomplishedusing a separate irrigation source which may pump into the ablationdevice or which may pump directly to the target tissue site. Thisrequires a separate device that may not deliver irrigation assite-specifically as desired.

[0009] Furthermore, there is relatively high hydraulic impedance tosaline flow at the distal end (towards ablation site) of a typicalablation device. In comparison, the hydraulic impedance to flow is lowerat the proximal end (towards user) of the device. This sometimes resultsin more irrigation fluid being distributed at the proximal end than atthe distal end.

[0010] Additionally, there may also be difficulties with electricalimpedance to saline flow in a typical ablation device. This may beparticularly true in a hemostat-type ablation device. In such a device,the target tissue is positioned between the two jaws of the hemostat,both of which carry ablation electrodes. If the tissue is shorter thanthe length of the hemostat jaws, a saline bridge may form between thehemostat jaws due to the surface tension of the fluid. This salinebridge is a low electrical impedance pathway. Electrical flow may,therefore, occur preferentially towards the bridge and yield unreliableablation.

[0011] Irrigation fluid may also not be evenly distributed along asingle electrode because of the impedance factors described above.Uneven distribution of fluid may result in an uneven lesion. In somecases, the tissue may not receive any irrigation in some areas. Theelectrode may contact the surface of the target tissue in theseunirrigated areas, causing sticking or even charring.

[0012] Additionally, longer electrodes are sometimes desired to createlonger lesions. These electrodes have a larger pressure drop along theirlength. This results in greater fluid flow from the proximal end thanthe distal end and thus irrigation is unevenly distributed which mayresult in sticking of the ablated tissue to the electrode. Currently anelectrode of a given length is needed to create a lesion of a givenlength. If a lesion of a different length is desired, a new electrodemust be used.

[0013] It would be desirable therefore to provide a means to control andvary irrigation.

[0014] It would further be desirable to facilitate control of lesionlength.

[0015] It would further be desirable to provide a means for evenlyirrigating an ablation electrode and concomitant target tissue site.

[0016] It would further be desirable to provide a means for evenlyirrigating ablation electrodes of variable length.

[0017] It would further be desirable to provide a device in whichirrigation capabilities and ablation capabilities are integrated.

SUMMARY OF THE INVENTION

[0018] One aspect of the present invention provides a device forablating organic tissue. The device includes a conductive element, afluid component in communication with the conductive element and anon-conductive interface positioned adjacent the tissue to allow thefluid to pass through the interface and contact the tissue. Theconductive element may be, for example, a metallic coil with a lumen, aspring with a lumen or a wire. The diameter of the conductive elementmay be greater than the diameter of the interface. The conductiveelement and the interface may be the same. The interface may bemicro-porous. The interface may also be of a variable length and aportion of the interface may be removable. The interface may beperforated, may comprise openings that are slidably or rotatably opened.The interface may be non-conductive or conductive. The interface may liebetween the conductive element and the tissue surface. The interface mayencircle the conductive element and the fluid component. The interfacemay be a rigid structure, a fluid saturated gel, or a micro-poroussection of the fluid component. The interface and the fluid componentmay be the same. The fluid component may be a non-porous coating. Thedevice may also include means for flowing the fluid component throughthe interface, such as an infusion pump.

[0019] Another aspect of the invention provides a device for creatingablations of variable length, comprising a conductive element having achannel formed therein, the channel operatively adapted to receiveirrigating fluid; and a removable non-conductive interface incommunication with the conductive element. The device may include asupport element in communication with the conductive element. Thesupport element may be a slotted tube. The conductive element may be aslotted tube.

[0020] Another aspect of the invention provides a device for creatingablations of variable length, comprising a non-porous tube operativelyadapted to receive irrigating fluid therein, a conductive element incommunication with the tube and a removable non-conductive interface incommunication with the conductive element. The non-conductive interfacemay be a portion of the non-porous tube. The non-conductive interfacemay be micro-porous. The non-conductive interface may be rigid.

[0021] Another aspect of the present invention provides a device forcreating ablations of variable length, comprising a non-porous tubeoperatively adapted to receive a hydrogel, a conductive element incommunication with the tube and a removable non-conductive interface incommunication with the conductive element. The non-porous tube may beslotted.

[0022] Another aspect of the present invention provides a method ofablating organic tissue. The method includes providing a conductiveelement having a channel formed therein, the channel operatively adaptedto receive irrigating fluid; and a removable non-conductive interface incommunication with the conductive element. The method also includesremoving a portion of the interface to expose a portion of theconductive element and ablating the tissue with the exposed portion ofthe conductive element. The interface may be perforated. The interfacemay be disposable. The interface may be reusable. The interface may alsobe a removable tip.

[0023] The foregoing, and other, features and advantages of theinvention will become further apparent from the following detaileddescription of the presently preferred embodiments, read in conjunctionwith the accompanying drawings. The detailed description and drawingsare merely illustrative of the invention rather than limiting, the scopeof the invention being defined by the appended claims in equivalencethereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a schematic view of a system for ablating tissue inaccordance with the present invention;

[0025]FIG. 2 is a longitudinal schematic view of a variable lengthablation electrode in accordance with the present invention;

[0026]FIG. 3 is a longitudinal schematic view of a second embodiment ofa variable length ablation electrode in accordance with the presentinvention;

[0027]FIG. 4 is a schematic view of a cross-section of a thirdembodiment of a variable length ablation electrode in accordance withthe present invention;

[0028]FIG. 5 is a longitudinal schematic view of a fourth embodiment ofa variable length ablation electrode in accordance with the presentinvention;

[0029]FIG. 6 is a longitudinal schematic view of a fifth embodiment of avariable length ablation electrode in accordance with the presentinvention;

[0030]FIG. 7 is a schematic view of a cross-section of one embodiment ofan ablation electrode in accordance with the present invention;

[0031]FIG. 8 is a schematic view of a cross-section of anotherembodiment of an ablation electrode in accordance with the presentinvention;

[0032]FIG. 9 is a schematic view of a cross-section of anotherembodiment of an ablation electrode in accordance with the presentinvention;

[0033]FIG. 10 is a schematic view of a cross-section of anotherembodiment of an ablation electrode in accordance with the presentinvention;

[0034]FIG. 11 is a schematic view of a cross-section of anotherembodiment of an ablation electrode in accordance with the presentinvention; and

[0035]FIG. 12 is a schematic view of a cross-section of anotherembodiment of an ablation electrode in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0036]FIG. 1 shows a schematic view of one embodiment of system 10 forablating tissue in accordance with the present invention. Typically thetissue to be ablated will be located within the body cavity, such as theendocardial or epicardial tissue of the heart. Other body organ tissue,such as the liver, can also be ablated using the present invention.System 10 may include an ablation device 20 that comprises at least oneconductive element 22, such as an electrode, and a connection 28 to apower source 30. System 10 also may include a conduit 38 to anirrigation source 40 that provides irrigation fluid to the ablationsite. System 10 may also include an insulating material 32 that mayinsulate conductive element 22. Insulating material 32 may also directdelivery of energy and/or irrigation along conductive element 22. System10 may also include a support member 33 that may provide structuralintegrity to conductive element 22. System 10 may also include anindifferent electrode 23 which may serve as the return plate for energytransmitted through electrode 22. Electrode 23 may also be covered byinsulating material and supported by a support member.

[0037] Ablation device 20 may be any suitable ablation tool such as, forexample, a catheter, an electrocautery device, an electrosurgicaldevice, a suction-assisted ablation tool, an ablation pod, an ablationpaddle, an ablation hemostat or an ablation wire. Ablation device 20 andits components are preferably made of a biocompatible material such asstainless steel, biocompatible epoxy or biocompatible plastic.Preferably, a biocompatible material prompts little allergenic responsefrom the patient's body and is resistant to corrosion from being placedwithin the patient's body. Furthermore, the biocompatible materialpreferably does not cause any additional stress to the patient's body,for example, it does not scrape detrimentally against any elementswithin the surgical cavity.

[0038] Preferably, ablation device 20 may be permanently or removablyattached to a maneuvering apparatus for manipulating device 20 onto atissue surface. For example, ablation device 20 may be attached tohemostat handles 12 such as shown in FIG. 1. Ablation device 20 may alsobe located on one or more of the hemostat jaws 32. Ablation device 20may also be used in conjunction with a traditional catheter, forexample, in a closed heart ablation procedure. Ablation device 20 mayalso be maneuvered with a leash or pull-wire assembly. Ablation devicemay also be positioned on a pen-like maneuvering apparatus such as theCardioblate pen available from Medtronic, Inc. Alternatively anyappropriate flexible or rigid handle could be used as a maneuveringapparatus. Alternatively, any appropriate endoscopic orthoroscopic-maneuvering apparatus may also be used with device 20.

[0039] Device 20 also preferably includes a connection 28 suitable forconducting energy to device 20, particularly to conductive element 22from a power source.

[0040] The conductive element 22 of ablation device 20 is preferably anelectrode. This electrode 22 may be positioned in any suitable place ondevice 20. Preferably electrode 22 is placed near an end of the device20, away from the user, to be more easily manipulated against the tissue60 to be ablated.

[0041] System 10 may also include an indifferent electrode 23 which mayserve as the return plate for energy transmitted through electrode 22.

[0042] Electrode 23 may be placed elsewhere on the patient's body thanthe ablation site. For example, electrode 23 may be placed on thepatient's back or thigh. Electrode 23 may also serve as a secondablation electrode in a bipolar arrangement. The two electrodes 22, 23may be arranged on the jaws of a hemostat-like tool such as shown inFIG. 1. Electrodes 22, 23 may be arranged in other orientations to eachother, such as, for example, parallel to each other on a surface.

[0043] As ablation occurs, it is sometimes desirable to irrigate theablation site with irrigation fluid, which may be, for example, anysuitable fluid such as saline or another conductive fluid. Theirrigating fluid may cool the electrode 22 of ablation device 20.Irrigated ablation is also known to create deeper lesions that are morelikely to be transmural. Transmurality is achieved when the fullthickness of the target tissue is ablated. Furthermore, continuous fluidflow may keep the ablation device surface temperature below thethreshold for blood coagulation, which may clog the device. Use ofirrigating fluid may therefore reduce the need to remove a cloggedablation device for cleaning or replacement. The presence of an ionicfluid layer between electrode 22 and the tissue to be ablated may alsoensure that an ionic fluid layer conforming to the tissue contours iscreated. In one preferred embodiment, saline solution is used.Alternatively, other energy-conducting liquids, such as Ringer'ssolution, ionic contrast, or even blood, may be used. Diagnostic ortherapeutic agents, such as lidocaine, CA⁺⁺ blockers, ionic contrast, orgene therapy agents may also be delivered before, with or after thedelivery of the irrigating fluid. Irrigation source 40 may be anysuitable source of irrigation fluid such as, for example, a standardirrigation pump (not shown). This pump may also be connected to powersource 30 or may have its own source of power. Preferably, device 20also includes a conduit 38 for delivering irrigation to the ablationsite from irrigation source 40.

[0044]FIG. 2 shows a schematic representation of one embodiment of avariable length electrode in accordance with the present invention.Electrode 222 may be covered with an insulating material 232. Prior toablation, insulating material 232 may be removed, for example, byrolling back towards a proximal end of electrode 222. As insulatingmaterial 232 is rolled back, ablating surface 242 of electrode 222 maybe revealed. The ablating surface may be applied against a surface oftissue 260. The length of ablating surface 242 may vary, depending onthe amount of insulating material 232 that is uncovered. Insulatingmaterial 232 is preferably a material that insulates the unexposed areaof the electrode 222. Such an insulating material may be, for example,silicone or polyurethane. The exposed ablation surface 242 may beconductive and irrigated. However, the section of electrode 222 coveredby insulating material 232 may be non-conductive. Furthermore, thesection of electrode 222 covered by insulating material 232 may beformed of a material that does not allow irrigating fluid to flowthrough. Since the irrigating fluid does not flow through the insulatedend, a saline bridge as described above may not form. Additionally, theinsulating material may direct all energy so that it is delivered to theexposed portion 242 of electrode 222. Additionally, the insulatingmaterial may direct all irrigating fluid so that it is delivered to theexposed portion 242 of electrode 222. The irrigation fluid may flowwithin the insulating material 232 but may not flow through the material232. Therefore, the unexposed, insulated portion of tool 20 may not beirrigated. The irrigating fluid may thereby delivered only to thedesired, exposed portion 242 of electrode 222.

[0045] Insulating material 232 may then be returned to its originalstate to cover exposed surface 242. The same electrode 222 may then beused to ablate a shorter surface. Alternatively, insulating material maybe a tip, which may be removed completely. A new insulating material maythen be placed over electrode. These tips of insulating material 232 maybe of variable length.

[0046]FIG. 3 shows a schematic longitudinal representation of anotherembodiment of the variable length electrode of the present invention. Inthis embodiment, insulating material 332 is perforated. In use, a usermay remove insulating material 332 from segment A, thereby exposingablation surface 342 as shown. If the user desires, a longer ablationsurface in order to create a longer lesion, he may remove additionalinsulating material 332 from segment B. This results in longer ablationsurface 343 as shown. Preferably insulating material that is removed maybe disposable.

[0047]FIG. 4 shows a cross-section view of another embodiment of thevariable length electrode of the present invention. In this embodiment,electrode 422 may be covered by insulating material 432 and a rotatingportion of insulating material 452. Portion 432 of the insulatingmaterial may cover most of the electrode 422. Electrode 422 may remaincovered by portion 432 of the insulating material along the length ofthe electrode. Meanwhile, portion 452 of the insulating material may beremovable or movable. Preferably, portion 452 may be rotatably removableor movable. In use, portion 452 of the insulating material may be movedto uncover ablating surface 442. For example, portion 452 of theinsulating material may be moved in the direction indicated by the arrowto remove the cover. Portion 452 may be moved to expose ablating surface442 of electrode 422 along the entire length of electrode 422.Alternatively, portion 452 of insulating material may be moved touncover ablation surface 442 only along a given portion of electrode422. Ablating surface 442 may be used to ablate a surface of tissue 460.

[0048]FIG. 5 shows a longitudinal schematic view of the variable lengthelectrode of the present invention. In use, the insulating material 532shown in FIG. 5 may be formed as a series of panels that cover electrode522. For example, three panels, A, B, and C are shown in FIG. 5. Panel Aof insulating material 532 may be moved to fit over panel B ofinsulating material 532. Panel A may be moved, for example, in thedirection indicated by the arrows. This may expose ablation surface 542which may have originally been covered by panel A. If the user desires alonger length electrode to create, for example, a longer lesion, theuser may slide panel B over panel C and panel A over panel B to exposean even longer ablation surface 543. Ablating surface 542, 543 may beused to ablate a surface of tissue 560.

[0049] In the embodiments shown in FIGS. 1-5, the conductive element maypreferably be a coil or spring. Alternatively, the conductive elementmay be metallic rod with a lumen machined into its axis, a wire braid, awire mesh or another suitable type of electrode.

[0050]FIG. 6 shows a longitudinal schematic view of a conductive element22 in accordance with the present invention. Preferably, the coil orspring may be made of a conductive material such as, for example, metal.This coil may have a lumen 24. Irrigating fluid may be flowed into thelumen 24 of coil 22. For example, irrigating fluid may be pumped fromirrigation source 40. As the fluid is pumped from irrigation source 40,the fluid may weep evenly along the length of the coil, thus deliveringfluid to the ablation site. A support member 33 may also be incorporatedinto or adjacent conductive element 22. Preferably support member 33provides conductive element 22 with additional structural rigidity. Thesupport member 33 may be, for example, a slotted metal tube. The supportmember may also be made from materials, such as, for example, Nitinol orother superelastic materials, which may allow support and somemalleability.

[0051] Slotted tube 33 may be formed of a slightly smaller diameter thancoil 22. In this case, a portion of coil 22 may protrude through theslot of tube 33 as shown at 630. This protruding of coil 22 may occuralong the length of electrode 22. Alternatively, this protruding mayoccur at a given area of electrode 22. This protrusion may help coil 22conform to the surface of tissue 660 to be ablated.

[0052] Preferably, the pitch or tightness of the coil of conductiveelement 22 may determine the current density of the conductive element22. Increasing the pitch of the coil (i.e. winding the coil lesstightly) may decrease the current density of the conductive element.Decreasing the pitch may increase the current density of conductiveelement 22.

[0053] Preferably, the pitch or tightness of the coil of conductiveelement 22 may determine the flow rate of the irrigation fluid throughthe conductive element 22. Increasing the pitch of the coil (i.e.winding the coil less tightly) may increase the flow rate of irrigationfluid through conductive element 22. Decreasing the pitch may decreasethe flow rate of irrigation fluid through conductive element 22.

[0054] As seen in the embodiment of FIG. 6, the coil 22 may be a doublecoaxial, reverse-wound spring. This embodiment, for example, provides anincreased resistance to fluid flow and nets a more even distributionalong the length of the coil. Therefore, by varying the pitch of aconductive coil 22, characteristics of the lesion created along thelength of the electrode may also be varied. Thus if a surgeon were todesire a shallower lesion at section F than at section G, he may use avariable pitch electrode as shown in FIG. 6. The decreased pitch atsection f of electrode 22 may result in a lower rate of irrigation flow.This may create a shallower lesion at section F of the tissue. Theincreased pitch at section g of electrode 22 may result in a higher rateof irrigation flow. This may create a deeper lesion at section G of thetissue.

[0055]FIG. 7 shows a schematic view of a cross-section of a variablelength electrode in accordance with the present invention. Conductiveelement 622 may be for example a double wound coil or spring asdescribed above. Irrigating fluid may be flowed through the lumen 724 ofelectrode 722. Support element 733 may be for example a slotted tube.Such a slotted tube 733 may be any suitable material that may provideadditional structural integrity to conductive element 722. The slottedtube 733 has an opening or slot 734. Preferably this opening 734 may runthe length of an entire conductive element 722. This opening 734 mayalso run the length of an exposed section of a conductive element 722which may be exposed in a manner as described in the above embodiments.This opening 734 may preferably face a surface of the tissue 760 to beablated. As shown in FIG. 7, insulating material 732 may cover a portionof conductive element 760 rather than covering the entire conductiveelement 722. Insulating material 732 may be for example a microporousnon-conductive component. Such a microporous non-conductive componentmay be manufactured from a material such as silicone, PTFE, Dacronfabric or solvent-precipitated polyurethane. Preferably, the pores inthe microporous non-conductive component may be large enough to allowthe free flow of irrigating fluid but small enough so as not to becomeclogged with protein or other detritus from the tissue to be irrigated.Irrigating fluid may flow from the lumen 724 of conductive element 722in the manner indicated by the arrows.

[0056]FIG. 8 shows a schematic view of a cross-section of a secondembodiment of a variable length electrode in accordance with the presentinvention. Conductive element 822 may be for example a double wound coilor spring as described above. Irrigating fluid may be flowed through thelumen 824 of electrode 822. Support element 833 may be for example aslotted tube. Such a slotted tube 833 may be any suitable material thatmay provide additional structural integrity to conductive element 822.The slotted tube 833 has an opening or slot 834. Preferably this opening834 may run the length of an entire conductive element 822. This opening834 may also run the length of an exposed section of a conductiveelement 822 which has been exposed in a manner as described in the aboveembodiments. This opening 834 may preferably face a surface of thetissue 860 to be ablated. As shown in FIG. 8, insulating material 832may cover all of conductive element 822. Insulating material 832 mayalso cover slotted tube 833. Insulating material 832 may be for examplea microporous non-conductive component. Such a microporousnon-conductive component may be manufactured from a material such assilicone, PTFE, Dacron fabric or solvent-precipitated polyurethane.Preferably, the pores in the microporous non-conductive component may belarge enough to allow the free flow of irrigating fluid but small enoughso as not to become clogged with protein or other detritus from thetissue to be irrigated. Irrigating fluid may flow from the lumen 824 ofconductive element 822 in the manner indicated by the arrows.

[0057]FIG. 9 shows a schematic view of a cross-section of a thirdembodiment of a variable length electrode in accordance with the presentinvention. Conductive element 922 may be a slotted tube that also servesas a support element. Irrigating fluid may be flowed through the lumen924 of electrode 922. The slotted tube 922 has an opening or slot 934.Preferably this opening 934 may run the length of an entire conductiveelement 922. This opening 934 may also run the length of an exposedsection of a conductive element 922 which may be exposed in a manner asdescribed in the above embodiments. This opening 934 may preferably facea surface of the tissue 960 to be ablated. As shown in FIG. 9,insulating material 932 may cover all of conductive element 922.Insulating material 932 may be for example a microporous non-conductivecomponent. Such a microporous non-conductive component may bemanufactured from a material such as silicone, PTFE, Dacron fabric orsolvent-precipitated polyurethane. Preferably, the pores in themicroporous non-conductive component may be large enough to allow thefree flow of irrigating fluid but small enough so as not to becomeclogged with protein or other detritus from the tissue to be irrigated.Irrigating fluid may flow from the lumen 924 of conductive element 922in the manner indicated by the arrows.

[0058]FIG. 10 shows a schematic view of a cross-section of a fourthembodiment of a variable length electrode in accordance with the presentinvention. Conductive element 1022 may be, for example a conductive wirelocated in a non-porous tube 1040. Irrigating fluid may be flowedthrough the lumen 1024 of tube 1040. The non-porous tube 1040 may have asegment of insulating material 1032. Preferably this segment 1032 mayrun the length of an entire conductive element 1022. This segment 1032may also run the length of an exposed section of a conductive element1022 which has been exposed in a manner as described in the aboveembodiments. This segment 1032 may preferably face a surface of thetissue 1060 to be ablated. Insulating material segment 1032 may be forexample a microporous non-conductive component. Such a microporousnon-conductive component may be manufactured from a material such assilicone, PTFE, Dacron fabric or solvent-precipitated polyurethane.Preferably, the pores in the microporous non-conductive component may belarge enough to allow the free flow of irrigating fluid but small enoughso as not to become clogged with protein or other detritus from thetissue to be irrigated. Irrigating fluid may flow from the lumen 1024 ofnonporous tube 1040 in the manner indicated by the arrows.

[0059]FIG. 11 shows a schematic view of a cross-section of a fifthembodiment of a variable length electrode in accordance with the presentinvention. Conductive element 1122 may be, for example a conductive wirelocated in a non-porous tube 1140. Irrigating fluid may be flowedthrough the lumen 1124 of tube 1140. The non-porous tube 1140 may have arigid segment 1132 of microporous non-conductive material. Preferablythis segment 1132 may run the length of an entire conductive element1122. This segment 1132 may also run the length of an exposed section ofa conductive element 1122 which has been exposed in a manner asdescribed in the above embodiments. This segment 1132 may preferablyface a surface of the tissue 1160 to be ablated. Rigid segment 1132 maybe, for example, a microporous non-conductive component that is rigid.Such a microporous non-conductive component may be manufactured from amaterial such as rod stock. Preferably, the pores in the microporousnon-conductive component may be large enough to allow the free flow ofirrigating fluid but small enough so as not to become clogged withprotein or other detritus from the tissue to be irrigated. Irrigatingfluid may flow from the lumen 1124 of nonporous tube 1140 in the mannerindicated by the arrows.

[0060]FIG. 12 shows a schematic view of a cross-section of a sixthembodiment of a variable length electrode in accordance with the presentinvention. Conductive element 1222 may be, for example a conductive wirelocated in a non-porous slotted tube 1233. Such a slotted tube 1233 maybe any suitable material that may provide additional structuralintegrity to conductive element 1222. The slotted tube 1233 has anopening or slot 1234. Preferably this opening 1234 may run the length ofan entire conductive element 1222. This opening 1234 may also run thelength of an exposed section of a conductive element 1222 which has beenexposed in a manner as described in the above embodiments. This opening1234 may preferably face a surface of the tissue 1260 to be ablated. Thelumen 1224 of tube 1233 may be filled with a material 1250 that exudesfluid such as, for example, a hydrogel. Irrigating fluid may be flowedthrough the hydrogel 1250 as described above. Alternatively, hydrogel1250 may be saturated with irrigating fluid. When hydrogel 1250 contactstissue 1260, gel 1250 may exude sufficient irrigating fluid. Tube 1233may be for example a microporous non-conductive component that is rigid.Such a microporous non-conductive component may be manufactured from amaterial such as rod stock. Preferably, the pores in the microporousnon-conductive component may be large enough to allow the free flow ofirrigating fluid but small enough so as not to become clogged withprotein or other detritus from the tissue to be irrigated. Irrigatingfluid may flow from the lumen 1224 of nonporous tube 1240 in the mannerindicated by the arrows.

[0061] It is contemplated that the electrodes of the present inventionmay be used in a variety of ablation systems such as those availablefrom Medtronic, Inc., Minneapolis, USA. It should be appreciated thatthe embodiments described above are to be considered in all respectsonly illustrative and not restrictive. The scope of the invention isindicated by the following claims rather than by the foregoingdescription. All changes that come within the meaning and range ofequivalents are to be embraced within their scope.

We claim:
 1. A device for ablating organic tissue, comprising: aconductive element; a fluid component in communication with theconductive element; and an interface positioned adjacent the tissue toallow the fluid to pass through the interface and contact the tissue. 2.The device of claim 1, wherein the conductive element is a metallic coilwith a lumen.
 3. The device of claim 1, wherein the conductive elementis a spring with a lumen.
 4. The device of claim 1, wherein theconductive element has a conductive element diameter and the interfacehas an interface diameter, the conductive element diameter being greaterthan the interface diameter.
 5. The device of claim 1, wherein theinterface has a length, the length being variable.
 6. The device ofclaim 1, wherein the interface is micro-porous.
 7. The device of claim1, wherein a portion of the interface may be removed to expose theconductive element.
 8. The device of claim 7, wherein the interface isperforated.
 9. The device of claim 7, wherein the interface may berotatably opened.
 10. The device of claim 1, wherein the interfacecomprises openings that may be slidably opened.
 11. The device of claim1, wherein the interface is non-conductive.
 12. The device of claim 1,wherein the interface is from the group consisting of: silicones, PTFE,Dacron fabrics, solvent-precipitated polyurethane micro-porous polymericcoatings, stainless steel nitinol, machining rod stock, polyesterfabrics, hydrogels and a gel.
 13. The device of claim 1, wherein theinterface lies between the conductive element and the surface of thetissue.
 14. The device of claim 1, wherein the interface encircles theconductive element and the fluid component.
 15. The device of claim 1,wherein the interface is conductive.
 16. The device of claim 1, whereinthe interface and the conductive element are the same.
 17. The device ofclaim 1, wherein the conductive element is a wire, the wire locatedwithin the fluid component.
 18. The device of claim 16, wherein thefluid component is a non-porous coating.
 19. The device of claim 16,wherein the interface is a micro-porous section of the non-porouscoating.
 20. The device of claim 16, wherein the interface is a rigidstructure.
 21. The device of claim 16, wherein the interface is a fluidsaturated gel.
 22. The device of claim 20, wherein the interface and thefluid component are the same.
 23. The device of claim 1 furthercomprising: means for flowing the fluid component through the interface.24. The device of claim 1 further comprising: an infusion pump incommunication with the fluid component for flowing the fluid componentthrough the interface.
 25. The device of claim 1 further comprising: amaneuvering mechanism operably attached to the conductive element. 26.The device of claim 25, wherein the maneuvering mechanism is ahemostat-type tool.
 27. The device of claim 25, wherein the maneuveringmechanism is a catheter.
 28. A device for ablating organic tissuecomprising: a conductive element; and a hemostat-type tool, wherein theconductive element is placed adjacent at least one jaw of the tool. 29.The device of claim 28, wherein the conductive element is a metalliccoil with a lumen.
 30. The device of claim 28, wherein the conductiveelement is a spring with a lumen.
 31. A device for creating ablations ofvariable length, comprising: a conductive element having a channelformed therein; the channel operatively adapted to receive irrigatingfluid; and a removable non-conductive interface in communication withthe conductive element.
 32. The device of claim 31 further comprising: asupport element in communication with the conductive element.
 33. Thedevice of claim 31, wherein the support element is a slotted tube. 34.The device of claim 31, wherein the conductive element is a slottedtube.
 35. The device of claim 31 further comprising: a maneuveringmechanism operably attached to the conductive element.
 36. The device ofclaim 31, wherein the maneuvering mechanism is a hemostat-type tool. 37.The device of claim 31, wherein the maneuvering mechanism is a catheter.38. A device for creating ablations of variable length, comprising: anon-porous tube operatively adapted to receive irrigating fluid therein;conductive element in communication with the tube; and a removablenon-conductive interface in communication with the conductive element.39. The device of claim 38, wherein the non-conductive interface is aportion of the non-porous tube.
 40. The device of claim 39, wherein thenon-conductive interface is micro-porous.
 41. The device of claim 38,wherein the non-conductive interface is rigid.
 42. The device of claim38 further comprising: a maneuvering mechanism operably attached to theconductive element.
 43. The device of claim 38, wherein the maneuveringmechanism is a hemostat-type tool.
 44. The device of claim 38, whereinthe maneuvering mechanism is a catheter.
 45. A device for creatingablations of variable length, comprising: a non-porous tube operativelyadapted to receive a hydrogel; a conductive element in communicationwith the tube; and a removable non-conductive interface in communicationwith the conductive element.
 46. The device of claim 45, wherein thetube is slotted.
 47. The device of claim 45 further comprising: amaneuvering mechanism operably attached to the conductive element. 48.The device of claim 47, wherein the maneuvering mechanism is ahemostat-type tool.
 49. The device of claim 47, wherein the maneuveringmechanism is a catheter.
 50. A method of ablating organic tissue,comprising: providing a conductive element having a channel formedtherein, the channel operatively adapted to receive irrigating fluid;and a removable non-conductive interface in communication with theconductive element; removing a portion of the interface to expose aportion of the conductive element; and ablating the tissue with theexposed portion of the conductive element.
 51. The method of claim 50,wherein the interface is perforated.
 52. The method of claim 50, whereinthe interface is disposable.
 53. The method of claim 50, wherein theinterface is reusable.
 54. The method of claim 50, wherein the interfaceis a removable tip.